November 12, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
3S5 
Chemical Composition. —Rose analysed the acid car¬ 
bonate prepared in different ways, and obtained results 
which led him to consider that the following- acid car¬ 
bonates existed:— 
co 2 oh,nh 3 
C0 2 ) 4 (OH 2 ) 5 (NH 3 ) 4 
C 0 2 ) 2 (OH 2 ) 3 (N H 3 ) 2 . 
But crystals like those to which he gave the second for¬ 
mula have a composition expressed by the first one, 
according to Berthollet, J. Davy, Deville and myself. 
The salt found by him to have the composition repre¬ 
sented by the third formula was a product of distillation 
once only obtained by him in small quantity. For this 
reason, and from a consideration and repetition of some 
of Rose’s methods of preparing carbonates by distillation, 
I am disposed to regard the existence of such a salt as 
extremely doubtful. 
Behaviour on Exposure. —It is probably quite fixed in 
dr}' air. In ordinary air it is very slowly dissipated, as 
was pointed out by Dalton. According to John Davy, 
it is decomposed by the atmospheric moisture, and ren¬ 
dered alkaline. Certainly, the moister it is, the more 
ammoniacal it renders the air confined with it in a bottle. 
By exposure to air, the faces of the crystals lose much of 
their lustre. It is not quite easy to recognize the nature 
of the change which the salt undergoes by exposure; 
for example, when the salt has been left for a while in a 
closed bottle, how is the strong smell of ammonia which 
is generated to be accounted for F What has become of 
the carbonic anhydride that was in combination with it ? 
Behaviour when Heated. —Like the normal carbonate, 
when heated in a retort, a little of it is first decomposed, 
and yields a few drops of liquid distillate, at about 49° 
C., which gradually crystallize in needles; while the 
rest, getting thus enveloped.in an atmosphere of the pro¬ 
ducts of this decomposition, undergoes no change at this 
heat. At about 60° it is slowly decomposed into carbonic 
anhydride, water and ammonia, the salt in the retort re¬ 
maining dry; but when the heat is carried much above 
60° C., the salt in the retort gets wet. The effect of heat 
is therefore thus represented :— 
C0 2 0H 2 NH 3 = C0 2 + OH 2 + NH 3 . 
Behaviour with Water. —As was first pointed out by 
Berthollet, the acid carbonate dissolves in about 8 parts 
of water, at 15° C. By exposure to the air this solution 
rapidly loses carbonic anhydride, but, as also pointed 
out by Berthollet, this loss is soon arrested. Gently 
heated, it effervesces. The solution placed in contact 
with solid acid carbonate decomposes it even at low tem¬ 
peratures, large bubbles of carbonic anhydride being- 
formed, as was pointed out by Davy, which adhere to the 
crystals, and, if the latter are small, carry them to the 
surface. A saturated solution of acid carbonate crystal¬ 
lizes out when cooled. 
Behaviour with Alcohol. —Acid carbonate is very 
slightly, if at all, acted on by strong aqueous spirit, cold 
or boiling. The crystals boiled with the spirit are 
slowly decomposed, as they would be by the heat alone ; 
carbonic anhydride and ammonia escape, and the remain¬ 
ing spirit is left weakened, and with a little caustic am¬ 
monia dissolved in it. 
Behaviour with Ammonia. —Dry crystals of the acid 
carbonate are not acted on by ammonia gas, either at 
ordinary temperatures or that of 0° C. When the pow¬ 
dered salt and strong solution of ammonia are brought 
together, a hissing sound is produced, the mixture be¬ 
comes warm, and the salt cakes together and shows little 
evidence of being dissolved. 
By digesting the acid carbonate with the strongest 
solution of ammonia in a closed vessel, at a temperature 
of 20 -25°, ammonium carbamate is slowly formed in 
considerable quantity. The mode of procedure is exactly 
similar to that already described for converting the nor¬ 
mal carbonate into the carbamate ; as are also the results, 
except that, as might be anticipated, the yield of the car¬ 
bamate is greater. In the first stage of the reaction, by 
which the carbamate is formed, the acid carbonate and 
the ammonia probably react, to form cai-bamate and nor¬ 
mal carbonate ; in the second stage, the normal carbonate 
thus formed changes into water, and carbamate, as was 
explained when treating of the reactions of the normal 
carbonate. Representing the change by a single equa¬ 
tion between the substances employed and those finally 
obtained, we have — 
CO,OH 2 NH 3 + NIL, = C0 2 (NH 3 ) 2 + OH 2 . 
(To he continued.') 
CYSTINE.* 
This rare substance has the composition C 3 H r N0 2 S ; 
it crystallizes in the form of six-sided plates, and forms 
with hydrochloric, nitric and phosphoric acids, definite 
crystalline compoimds. 
Dr. Bence Jones has shown that nitrous acid decom¬ 
poses cystine with evolution of nitrogen, the sulphur it 
contains being oxidized to sulphuric acid, whilst a non¬ 
crystalline substance is left which is precipitable by 
nitrate of silver, mercuric chloride, or acetate of lead. 
The cystine used in the author’s experiments was ob¬ 
tained by treating pounded calculi with strong liquor 
ammonia?, which dissolved the greater part, then evapo¬ 
rating the solution at a very gentle heat. The cystine 
which separated was again dissolved in ammonia and re¬ 
crystallized. 
Hydrochlorate of Cystine, — obtained by dissolving- 
cystine in boiling hydrochloric acid, separated on cool¬ 
ing as beautiful needle-shaped crystals, very soluble in 
water. When thoroughly dried in vacuo over quick¬ 
lime, the crystals were found not to be readily soluble in 
water. 0-05 gram of crystalline hydrochlorate of cystine 
yielded 0-0452 gram of AgCl, corresponding to 22 - 2 per 
cent, of HC1 (calcined 22’5). 
When cystine is dissolved in strong solution of ammo¬ 
nia, and a solution of silver nitrate in ammonia added, 
no precipitate is formed, nor does the solution darken in 
the cold. When slightly acidified with nitric acid, a 
canary-yellow precipitate is thrown down. The filtrate 
blackened when heated, and on filtering off the black 
precipitate a clear colourless solution was obtained, which 
was not further blackened when boiled with ammoniacal 
solution of oxide of silver. On analysis the yellow sub¬ 
stance proved to be a compound .of cystine with nitrate 
of silver. 
In a subsequent experiment an ammoniacal solution of 
cystine was boiled with an ammoniacal solution of nitrate 
of silver. A black precipitate fell which consisted of 
sulphide of silver. The filtrate from the precipitate of 
sulphide of silver was subsequently treated with solution 
of chloride of ammonium to separate the excess of silver. 
The solution was found not to be precipitated by hydro¬ 
chloric acid and chloride of barium nor by sulphate of 
calcium. It is therefore evident that when an ammo¬ 
niacal solution of cystine is heated with ammoniacal so¬ 
lution of oxide of silver, the sulphur is separated entirely 
as sulphide of silver, none being oxidized; it is also ob¬ 
vious that no oxalic acid is formed. 
Cystine, treated with NaHO, and evaporated in a 
silver basin, gives a reddish liquid; sulphide of sodium 
is then produced, blackening the basin, and ammonia is 
copiously evolved. On treating the residue with water, 
neither sulphuric nor oxalic acids can be detected, but 
the liquid contains a large quantity of sulphide of sodium 
with a mere trace of sulphite. 
Cystine, heated to 150° C. with solution of caustic 
baryta in sealed tubes, gives off ammonia, a large quan- 
* Abstract from a paper by James Dewar, F.R.S.E., 
Lecturer on Chemistry, Veterinary College, Edinburgh; and 
Arthur Gamgee, M.D., F.li.S.E., Lecturer on Physiology at 
Surgeons’ Hall, Edinburgh, published in the Proceedings ot 
theltoyal Society of Edinburgh, 1809-70. 
